Re: mixing waveforms... like for a synthesizer

On Mar 28, 1:00 pm, et...@xxxxxxxxxxxxxxxxxxx (Michael Black) wrote:
panfilero (panfil...@xxxxxxxxx) writes:
This may be a really simple question, but I was wondering what is the
correct way to mix 2 or more waveforms. For example if I want to mix
a sine wave and a sawtooth wave in order to produce an audio tone.
So, lets say I have a sine wave of a a few millivolts and a sawtooth
of about the same amplitude and nearly the same frequency and both of
them are signals which can independently drive a little speaker... but
now I would like to mix the two signal and listen to the resulting
signal. If both of those signals are the outputs of two different
pins or wires... do I just connect the two wires together? I don't
think that's the right way to do it for some reason... but I'm not
sure what is.

But what are you trying to do?

Create a signal with two different sounds, or create a different sound?

The first is simple "mixing". Just like in a recording studio, where
they have multiple microphones and sound sources (from electric instruments),
and they are mixed together to get the total sound. IN that case, they
are just summed together. The usual thing is a an op-amp configured as
an inverting amplifier, and then instead of one input resistor, there
are multiple resistors, one for each sound source. Usually, there is a pot
before each of those resistors, so the sound level of each "channel" can
be adjusted.

If you are trying to create a new sound, then you need something more
complicated. But keep in mind that in analog synthesizers, the usual
method is to start with a sawtooth waveform, and then filter to get the
right waveform. Or pick the an appropriate waveform, square, pulse or
maybe triangle, which may make the actual adjustments simpler.

Digital changes it all.

But if you are creating a new waveform, the output will not contain
the two original waveforms, and you can't simply "mix" them together
like in the first case.

Explain what you really want, and you'll get an answer.

Michael

OH, I didn't know that it was different... I would like to create a
new sound out of the mixed waveforms (am I wrong to use the words
waveforms and signals interchangeabley?) I was thinking that mixing
the two signals would output a new different signal that would be the
sum of the original two signals....

When you mention sending them to an op-amp, are the two signals mixed
at the inverting input of the op-amp? And the opamp then just
amplifies the already mixed signal?

Thanks
.

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